Autofill is the feature of Excel that can be used to fill a series of data continuously through rows and columns without typing.  The active cell contains a black dot at lower right corner that is known as Fill Handle. 

Fill handle can also used to copy cell content to another cell.  Fill handle can be used either horizontally or vertically.

Using AutoFill to fill series of numeric data:

1. Enter two numbers in the series
2. Select both cells
3. Place mouse pointer on Fill handle of active cell
4. drag to fill remaining numbers in the series.

Using Autofill to fill Custom List:

1. Office button–>excel options–>popular–>Edit custom lists
2. Click in List Entries box
3. Enter each custom list entry followed by enter
4. click add the created custom list to Excel–>click OK
5. type any one entry of your list in a cell
6. use fill handle to fill remaining entries